Figure 4: Macroscopic findings of the osteochondral defects in knees. The defects of both the left and right knees induced production of regenerated tissues that were pearly white and firm at 12 weeks post operation. After treatment with human umbilical cord mesenchymal stem cells and hyaluronic acid (right knee), the regenerated tissues were adherent to the adjacent cartilage and restored the appearance of the femoral condyles (smooth articular surface). The control knee (left knee) showed that the regenerated tissues were fibrillated and that the hole was obviously deepening